Soil penetrating tool assemblies are commonly used in the agricultural industry to break up soil to facilitate sowing of seeds or for other soil preparation procedures. The tool assemblies often include a shank which is sharpened at one end or alternatively provided with a soil penetrating tool and the shanks are mounted to a cultivator frame that is pulled by a tractor through a draw bar or mounted to a tool bar that is attached to the tractor by means of a three point hitch.
It has been common for the shanks of the tool assemblies to be releasably mounted to prevent damage to the shanks, frame, tool bar and/or the shank carrying implement when an obstruction is encountered in the soil.
Various devices have been used to attach tool assemblies and shanks to a cultivator frame. In one common configuration, a clamping assembly is clamped or bolted to the frame and the shank supported in a yoke to the clamping assembly by a mounting pin or bolt and a shear pin extending through sets of aligned holes. Where excessive obstructions or loads in the ground are encountered, the shank may pivot and cause the shear pin to break. In such arrangements and in other arrangements where shear pin systems are used, the breakage of a shear pin necessitates stopping the prime mover and replacement of the shear pin to enable ploughing to be recommenced.
Other arrangements have provided a spring system wherein a spring applies a biasing force to the shank to maintain the shank in the ground. The spring, however, normally is required to be of such a size as to exert as high as possible force on the shank to maintain it in the ground. Sufficient force to maintain the digging point in the ground in hard compacted soils would require springs of huge and impractical sizes.
Other systems have used hydraulic rams as a means for opposing movement of the shank out of the ground. These systems would require huge and impractical hydraulic rams to maintain penetration in hard compacted soils. Such large rams or large springs also subject the digging points and shanks to possible breakage during the obstruction jumping action when the shanks and points are in the raised non digging configuration. Furthermore, springs and rams in the above configurations are arranged to exert a force on the shank in such a manner that all movements of the shank will be opposed by the same force.
The present invention aims to overcome or alleviate one or more of the above described disadvantages or at least provide an alternative to the soil penetrating tool assemblies of the type described above. Other objects and advantages will become apparent from the following description.